1. Field of the Invention
The present invention related to a field of recovery and reuse of poly(vinyl butyral) material, and more particularly to a method of producing poly(vinyl butyral laminate from a discarded laminated glass.
2. Description of the Prior Arts
Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheet that can be used as interlayers in light-transmitting laminates. Safety glass and windshield glass are composed of two glass plates and a poly(vinyl butyral) sheet interposed between the glass plates or alternatively composed of a single glass plate and a poly(vinyl butyral) sheet assembled therewith, and then the assembly is subjected in an autoclave to about 90° C. to 165° C. at pressure of about 1034 to 2067 kPa for at least 10 minutes to tightly bond the glass plate with poly(vinyl butyral) sheet, and then form the safety and windshield glass.
The poly(vinyl butyral) sheet can be produced by mixing poly(vinyl butyral) resin with one or more plasticizers, and optionally with one or more other ingredients, and melt processing the mixture into a sheet, which can be collected and rolled for storage and transportation. With adherence and impact strength of the poly(vinyl butyral) interlayer, safety and windshield glasses are crumbled into several small granular glass chunks instead of sharp shreds when broken.
Poly(vinyl butyral) is typically produced by a complicated synthesis, including separation of ethane from natural gas, dehydrogenation of ethane to produce ethylene, polymerization of vinyl acetate monomers to form poly(vinyl acetate), hydrolization of poly(vinyl acetate) to form poly(vinyl alcohol) and reaction between poly(vinyl alcohol) with butyraldehyde. Therefore, said chemical synthesis of poly(vinyl butyral) is expensive, environmentally unfriendly and not applicable for mass production. Thus, techniques of recycling the reusable poly(vinyl butyral) from laminated glass have been developing.
Some methods that recycle of poly(vinyl butyral) from a discard laminated glass and utilization of the recycled poly(vinyl butyral) are described in U.S. Pat. No. 7,521,107, which discloses a method of utilizing recovered poly(vinyl butyral) in the production of carpet backcoatings. However, the patent only mentions PVB can be separated and recovered from used or discarded safety glass via commercial windshield glass recycling methods, and does not teaches how to recycle the discarded safety glass in an environmentally friendly way.
U.S. Patent Appl. Pub. No. 2009/0209667 discloses a method of recycling poly(vinyl butyral) resin from safety glass. However, the method includes a solvent extraction of plasticizer and impurities and dissolution of poly(vinyl butyral) interlayer in organic solvents, such that a large amount of organic solvent waste and severe environmental contaminations are produced.
U.S. Patent Appl. Pub. No. 2010/0249253 also discloses a method of recycling of poly(vinyl butyral) from laminated glass. The laminated glass is shattered first to separate a poly(vinyl butyral) sheet from the laminated glass. The obtained poly(vinyl butyral) sheet is further cut into pieces, then proceeding to a surface cleaning process to eliminate the dirt and impurities. However, the method as disclosed requires a final chemical treatment for purification, and thereby resulting similar drawbacks as mentioned above.
There remains a need for recycling the reusable poly(vinyl butyral) material from the laminated glass in an environmentally friendly way to mitigate or obviate the aforementioned problems.